I have a 2002 hydrodyne v drive boat with a 2007 mercruiser 350 mag mpi and Walter v drive... Today was my first day on the lake for the season, and the boat ran great for about 4 hours tubing, wake boarding ect, then when just cruising down the lake there was a loss of power (like it went to idle out of nowhere) and a alarm sounded. I stopped the boat checked all fluids and sat for a few minutes. Started it back up and it ran fine for 15 minutes or so before losing power again. No alarm this time. Decided to limp back to the marina where this happened a few more times and the engine even shut off a time or two. Finally I decided just to catch a tow so I didn't screw anything else up. The engine temp wasn't looking bad (165) and after sitting a few minutes it would start right up, but shut off sooner and sooner each time. My first thought was impeller, but I am not sure if that could be it without the engine temp rising?? Any help\opinion would be great

I have a 01' tige with basically the same engine. I had that happen to me because we were working the engine too hard in 100+ weather. I had ballast and about 10 people on board at the time. I really don't remember seeing the engine temp gauge get hot or anything. I ended up floating in a cove for awhile, letting engine cool down. Never had a problem since. I think the engine temp sensor is right at the water manifold that gets mixed with cool raw water right away. Maybe things just got a little hot. But more importantly find out why your engine was working hard. Bilge full of water? Ballast? Wrong prop?

Thanks for the quick response! I have only had this happen once before when I was taking on water so I definitely checked the bilge right away. Ballasts were empty and the same prop that's been on it for years. There has to be some problem I'm just not sure where to start. I have a scan tool and it was reading coolant temp of 165 degrees and the gauge agreed with it so if anything was hot it would have to be the transmission.

Check the impeller.. It might be missing 2 or 3 blades and can still cool the engine.. The problem is the missing blades clog the trans cooler and the tranny oil will over temp.. That will put it in limp mode..

Thanks for the input! I will check the impeller tomorrow and hope that's it cause I'm not that much of a wiring guy! Fuel pump will be my next check, but do you know if that can send it into protection mode as well? Thanks again!

Today was my first day on the lake for the season, and the boat ran great for about 4 hours tubing,

Tubing obviously broke it.

Assume this is a 555? My 02 merc is very picky and loves to limp mode at the slightest sneeze of an issue. The list of issues it could be is not worth part chasing. My advice is to get it scanned at a shop. My shop charges a very small fee to just hook it up and see what caused the limp mode. Takes a grand total of 10 minutes to hook it up and find a definitive issue. To me its not worth the time ripping crap apart or part chasing.

if you chose not to do so check to make sure the connection at your lp and hp fuel pumps are tight especially at the deutch connectors. Also check your screen by your sea water sensor. You can get a small piece of crap or impeller stuck in it and you will read low pressure there. it takes less time to check the screen that the actual impeller. If the impeller imploded it will be sitting there.

As dumb as it sounds I'm not sure. It's the 350 mag mpi tow sports engine the boat is new to me as of last fall. I have a merc scan tool and got these codes this morning but I've seen the first 3 before I'm pretty sure they are just unused features but could be wrong...

Now with the engine running at idle I am seeing two codes I have never seen before. The codes are Fault 19 over speed and
Fault 10 knk snsr1. I'm guessing those don't sound good... Something a mechanic would have to fix engine troubles etc, or just a Sensor?

The fault 10 knk snsr1 is most likely your fault but doesn't mean alot. The others are most likely ghosts that are caused by not having those sensors. I can't tell you positively about that b/c I'm not in your boat and with it being an aftermarket engine weird chit happens. Trust me I have a merc in a MC and I have plenty of the same ghost codes. The last code you describe is your knock sensor. This is a slam your head into a wall code. It could be bad gas, iac, tps, a bad knock sensor or a slew of other small issues. Don't scare yourself into thinking the engine is imploding.

2 questions before I tell you to go have it hooked up on a comp again

1) Have you changed the distributor cap lately? Reason I ask is there were a handful of shotty caps that got circulated that crossfired.

2) Are you sure you didn't overheat?

Sounds like you are freaking out a bit. Take a deep breath and realize this is the nature of that engine especially when it lives in a home it wasn't designed for. Call your local mechanic and ask how much he'd charge to throw it on the computer for a hot minute. its probably going to take him 5 minutes to tell you whats wrong based on you having a steady occurence of the problem.

I can tell you this. When you ask how much a part is you are parts chasing and that won't get chit done in a boat. You will empty every pocket trying to resolve an issue that way and end the day being more frustrated. You can go google any issue on the planet regarding a merc and get 100 different situations and theres a reason for that.

Anthony, What's the price, and how hard to switch? Did yours have a knock code, and lose power with alarm out of nowhere? Thanks a ton!

Also just fyi you are going to have power loss almost regardless of any issue you ever have on that engine. If you have low fluids.......guardian. If you have low fuel pressure........guardian. Its mercruisers way of protecting you from imploding your engine. Its a great feature but highly frustrating at times.

William, Thanks for all your help. The distributor cap has not been changed that I know of. I just got the boat last October so I have only had about 10 days on the water. I am pretty sure I didn't overheat (the engine atleast) because when it happened I wasn't pulling anything within 30 min of it happening, and the gauge as well as scan tool read the temp to be good.
The boat is at a marina on a lift right now which is why I was hoping to find a fix, but if this code could be for any number of things I may be better off getting a tow and pulling it to a shop. Will their computer be able to tell exactly what part is bad instead of just a general code? Thanks a ton WakeWorld seems to have an amazingly helpful and informative forum

I have had the same thing happen on two different occasions and both time it was a BAD IAC. They are know to fail on the Merc 350s. easy to replace.

That is very true. They are also around 130 bucks. I have a spare one in my garage from when I thought I diagnosed a bad iac and it wasn't it. Can go test it though

Quote:

but if this code could be for any number of things I may be better off getting a tow and pulling it to a shop.

You can throw an iac on it and try it but its less than a coin flip imho. If its on a lift call a local mechanic and ask if they'll come to you. My mech has come on my boat no prob for super weird issues. The problem is you can spend 120 bucks on an IAC and it might not solve the problem when it would cost you that much to know for sure. Then what happens? You end up taking it to a shop and throwing it on the computer anyways. I have no doubt it could be an iac but thats your call. I don't know your financials or what you intend to do with the boat. Yes iac's are crap on those engines and yes at some point you will probably need one. So you can try it and put it on a shelf somewhere if thats not the problem. If you don't mind a 120 dollar part collecting dust then go for it. Most likely your local merc guy will have 10 on the shelf.

You can also check it or clean it before you buy a new one if you want to try one more thing.,

pm sent. I may have given you some meh advice. Might as well check the iac. Didn't think about that being testable. Anything beyond a quick test and I would move on to having it slapped on the computer.

If the IAC was bad would it idle normal? mine does, but it seems like if it was bad it would not be a steady idle. I will probably check in with the local merc mechanic and see what he would charge to go hook it up!

The IAC on these engines are crap, they never work right. I've changed 3 of them in ten years. My TPS sensor installed at AWS in Oregon cost me 225.00
If you change it yourself, you will save labor. It was detected by AWS with a scan. Not sure what the code was......

Hey William sorry for the slow response. I cleaned out that line by the Dizzy as you suggested, and it has been running great ever since. there was a little junk (weeds etc.) but not a ton. not sure if that did the trick, or if the tubing got the trans hot or something. Just hoping the smooth sailing continues! thanks for the help!